What is in the spark

When I take a step-up transformer say from the igniter coil from an oil burner and step up the voltage from 110 volts to 10,000 volts with just a very small fraction of an amp in the secondary why is it I get a huge spark. Is the spark not a large collection of electrons jumping the gap because of the high voltage applied to them? And if so that many electrons flowing across the gap should register as a high current at that space in time, yet it does not. If this is not electron flow, what is it?